Apparatus for collecting solar energy for conversion to electrical energy

ABSTRACT

The present disclosure provides an apparatus for collecting solar energy for electrical energy generation through one or more thermodynamic closed-cycle heat engines or the like. The present invention includes new designs for solar collectors that concentrate solar energy, and mechanisms for transporting and transferring the concentrated solar energy directly into the working fluid (e.g., a liquid, a gas, or a phase change substance) of the closed cycle thermodynamic engines without heating the outside surface of the engines. In an exemplary embodiment, the present utilizes an inflatable design for a dual-surface reflector which provides low cost and weight, protection from external elements, and the ability to inflate/deflate as required.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present non-provisional patent application claims priority to U.S.Provisional Patent Application Ser. No. 60/993,946, filed Sep. 17, 2007,entitled “METHOD AND APPARATUS FOR CONVERTING SOLAR ENERGY INTOELECTRICAL ENERGY,” to U.S. Provisional Patent Application Ser. No.61/011,298, filed Jan. 16, 2008, entitled “METHOD AND APPARATUS FORCONVERTING SOLAR ENERGY INTO ELECTRICAL ENERGY USING CLOSED-CYCLETHERMODYNAMIC ENGINES AND PIEZO-ELECTRIC GENERATORS,” to U.S.Provisional Patent Application Ser. No. 61/063,508, filed Feb. 4, 2008,entitled “METHOD AND APPARATUS FOR CONVERTING SOLAR ENERGY INTOELECTRICAL ENERGY USING MULTIPLE CLOSED-CYCLE THERMODYNAMIC ENGINE ANDPIEZO-ELECTRIC GENERATORS,” and to U.S. Provisional Patent ApplicationSer. No. 61/066,371, filed Feb. 20, 2008, entitled “METHOD AND APPARATUSFOR CONVERTING ELECTROMAGNETIC ENERGY INTO ELECTRIC AND THERMAL ENERGYUSING A CLOSED-CYCLE THERMODYNAMIC ENGINE AND ELECTRIC GENERATOR,” allof which are incorporated in full by reference herein.

FIELD OF THE INVENTION

The present invention relates generally to solar energy. Moreparticularly, the present invention provides an apparatus for collectingsolar energy for use in electrical energy generation throughclosed-cycle thermodynamic engines or the like.

BACKGROUND OF THE INVENTION

Solar energy is one of the renewable energy sources that does notpollute, it is free, and available virtually everywhere in the world.For these reasons, over the years there have been many systems andmethods that attempted to utilize solar energy and convert it into otherusable forms of energy such as electricity. More recently, due toperceived shortages and higher prices of fossil fuels and due topollution concerns, the interest has increased and the pace ofdevelopment of technologies that utilize alternative energy sources(such as solar) has accelerated.

There are two main techniques developed to harvest solar energy. Thefirst technique utilizes photovoltaic solar cells to directly convertsolar energy into electricity. The photovoltaic solar cells have theadvantage of small size, but are expensive to manufacture and the priceper watt has leveled due to the high cost of the semiconductor substrateutilized to construct the photovoltaic solar cells. There are many typesof designs and materials used to make photovoltaic solar cells whichaffect their cost and conversion efficiency. Current commerciallyavailable solar cells typically reach a starting efficiency around 18%which drops over time. The cells produce direct current (DC) that needsto be regulated, and for higher power applications typically the DCcurrent also needs to be converted to AC current.

The second technique utilizes the heat (infrared radiation) associatedwith the solar energy. Assuming that the goal is to generate electricalenergy, the solar radiation gets collected, concentrated, and utilizedas a heat source for various systems that convert the heat intomechanical energy, which is then converted into electrical energy.Successful machines developed to convert heat into mechanical energy canbe based on thermodynamic cycles such as the Stirling cycle and theRankine cycle or variations of these. Mechanical energy produced bythese machines is further converted into electrical energy by usingrotating generators or linear generators. For example, in the case of aStirling engine, heat (which can come from any heat source) is appliedat one end of the engine and cooling is provided at a differentlocation. The working fluid (gas), which is sealed inside the engine,goes through a cycle of heating (expansion) and cooling (contraction).The cycle forces a piston inside the engine to move and producemechanical energy. When the heat source is solar, successful enginedesigns use an intermediate medium such as molten salt to more uniformlydistribute the heat around the outside surface of the heating end of theengine.

With respect to the second technique and more specifically referring toStirling engines, problems arise when the surface of the engine isexposed to large temperature gradients due to close proximity of theheat and cooling sources on the surface of the engine. For example,conventional engines can see extreme temperatures from day to night andalong the length of the engine body with temperatures ranging from over1000 degrees Fahrenheit to room temperature across the engine body.Disadvantageously, these types of engines face difficult materialproblems such as weld joint cracking and loss of material properties dueto thermal cycling over time. Also, there are losses associated withheat radiation from the hot end of these types of engines leading toinefficiency. The other type of cycles, such as Rankine which is used todescribe steam turbine operation, is suitable only for large solar powerplants with minimum power in the multi tens of MW range. These solarpower plants are expensive and have a number of other problems such asmaintenance of the reflecting optical surfaces.

BRIEF SUMMARY OF THE INVENTION

In various exemplary embodiments, the present invention provides anapparatus for collecting solar energy for electrical energy generationthrough one or more thermodynamic closed-cycle heat engines. The presentinvention includes new designs for solar collectors that concentratesolar energy, and mechanisms for transporting and transferring theconcentrated solar energy directly into the working fluid (e.g., aliquid, a gas, or a phase change substance) of the closed cyclethermodynamic engines without heating the outside surface of theengines. In an exemplary embodiment, the present utilizes an inflatabledesign for a dual-surface reflector which provides low cost and weight,protection from external elements, and the ability to inflate/deflate asrequired.

In an exemplary embodiment of the present invention, a dual-surfacereflector for collecting solar energy includes a primary reflector; asecondary reflector configured to receive solar energy reflected fromthe primary reflector and concentrate the solar energy; and an openingin the primary reflector, wherein the concentrated solar energy isprovided by the secondary reflector to the opening; wherein the primaryreflector and the secondary reflector each include inflatablecomponents. The dual-surface reflector can further include a switchlocated at the opening, wherein the switch is configured to distributethe concentrated solar energy to one or more thermodynamic engines.Optionally, the dual-surface reflector further includes a support ringdisposed around the edges of the primary reflector, wherein the supportring is configured to maintain a shape of the primary reflector. Thedual-surface reflector can further include a transparent and flexiblematerial disposed between the primary reflector and the secondaryreflector, wherein the transparent and flexible material issubstantially optically transparent in the infrared region. Thetransparent and flexible material forms a seal between the primaryreflector and the secondary reflector providing protection from externalelements. Optionally, the transparent and flexible material includesfluorinated ethylene propylene. The dual-surface reflector can furtherinclude a base supporting the primary reflector; and a trackingmechanism to point the primary reflector towards the sun. Optionally,the dual-surface reflector further includes an air pump configured toinflate the inflatable components. The dual-surface reflector can alsofurther include a valve for connecting the air pump to the inflatablecomponents and for deflating the inflatable components; and amicrocontroller configured to control the air pump and the valve.Optionally, the primary reflector and the secondary reflector eachinclude fluorinated ethylene propylene with a thin, highly reflectivemetal layer.

In another exemplary embodiment of the present invention, a dual-surfaceinflatable reflector for collecting solar energy includes an outersupport ring; a primary reflector disposed to the outer support ring; asecondary reflector configured to receive solar energy reflected fromthe primary reflector and concentrate the solar energy, wherein thesecondary reflector is disposed to a transparent and flexible materialdisposed to the outer support ring; and an opening in the primaryreflector, wherein the concentrated solar energy is provided by thesecondary reflector to the opening; and inflation means for inflatingthe outer support ring and an interior formed between the primaryreflector, the opening, the secondary reflector, and the transparent andflexible material. The dual-surface inflatable reflector can furtherinclude solar tracking means for pointing the primary reflector towardsthe sun. Optionally, the dual-surface inflatable reflector furtherincludes switching means for distributing the concentrated solar energyto one or more thermodynamic engines. The transparent and flexiblematerial forms a seal between the primary reflector and the secondaryreflector providing protection from external elements. Optionally, thetransparent and flexible material includes fluorinated ethylenepropylene.

In yet another exemplary embodiment of the present invention, a methodof operating a solar collector includes inflating a reflector with apump; positioning the reflector towards the sun; collecting solar energywith the reflector; concentrating the solar energy to an opening; anddistributing the solar energy to one or more engines. The method canfurther include deflating the reflector responsive to one of adeactivation signal and a determination of inclement weather.Optionally, the method further includes storing the reflector in a base.The reflector can include a primary reflector; a secondary reflectorconfigured to receive solar energy reflected from the primary reflectorand concentrate the solar energy; and an opening in the primaryreflector, wherein the concentrated solar energy is provided by thesecondary reflector to the opening; wherein the primary reflector andthe secondary reflector each comprise inflatable components. Optionally,the primary reflector and the secondary reflector each includefluorinated ethylene propylene with a thin, highly reflective metallayer.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated and described herein with referenceto the various drawings, in which like reference numbers denote likesystem components and/or method steps, respectively, and in which:

FIG. 1 is system schematic including a dual-surface reflector forcollecting and concentrating solar energy according to an exemplaryembodiment of the present invention;

FIG. 2 are multiple low-profile solar collectors for providing a flatterand compact low-profile arrangement according to an exemplary embodimentof the present invention;

FIG. 3 is a mechanism for combining solar radiation from multiplelow-profile solar collectors through light guides according to anexemplary embodiment of the present invention;

FIG. 4 is a diagram of various designs for a focusing/collimatingelement according to an exemplary embodiment of the present invention;

FIGS. 5A and 5B are partial cross-sectional views of a thermodynamicclosed-cycle based engine according to an exemplary embodiment of thepresent invention;

FIG. 6 is a diagram of an energy distribution and delivery system forconcentrated solar energy directly into thermodynamic closed-cycle basedengines according to an exemplary embodiment of the present invention;

FIG. 7 is a flowchart of an energy distribution and delivery mechanismfor concentrating and releasing solar energy in a pulsating mannerdirectly into thermodynamic closed-cycle based engines according to anexemplary embodiment of the present invention; and

FIG. 8 is a flow chart of a mechanism to convert solar energy intoelectric energy according to an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

In various exemplary embodiments, the present invention provides anapparatus for collecting solar energy for electrical energy generationthrough one or more thermodynamic closed-cycle heat engines. The presentinvention includes new designs for solar collectors that concentratesolar energy, and mechanisms for transporting and transferring theconcentrated solar energy directly into the working fluid (e.g., aliquid, a gas, or a phase change substance) of the closed cyclethermodynamic engines without heating the outside surface of theengines. In an exemplary embodiment, the present utilizes an inflatabledesign for a dual-surface reflector which provides low cost and weight,protection from external elements, and the ability to inflate/deflate asrequired.

Referring to FIG. 1, a dual-surface reflector 100 is illustrated forcollecting and concentrating solar energy 102 according to an exemplaryembodiment of the present invention. The dual-surfaces on thedual-surface reflector 100 include a primary reflector 104 and asecondary reflector 106. The reflectors 104, 106 can be in a parabolicshape, a spherical shape, and the like. Also, the secondary reflector106 can be concave or convex depending on the positioning of thesecondary reflector 106 relative to the primary reflector 104. Theprimary reflector 104 is pointed towards the solar energy 102, and thesecondary reflector 106 is located above the primary reflector 104. Theprimary reflector 104 is configured to reflect the solar energy 102 tothe secondary reflector 106 which in turn concentrates the solar energy102 through an opening 108 at a center of the primary reflector 104.

An outer perimeter support ring 110 is disposed around the edges of theprimary reflector 104 to maintain the shape of the primary reflector 104and to anchor in place the primary reflector 104. A transparent andflexible material 112 connects to the primary reflector 104 and to thesupport ring 110 to hold the secondary reflector 106 in place. Thetransparent and flexible material 112 is configured to allow the solarenergy 102 to pass through, and can be constructed from a material thatis optically transparent in the infrared region, such as a material inthe Teflon® family of products, for example, fluorinated ethylenepropylene (FEP) or the like. The transparent and flexible material 112provides a closed design of the dual-surface reflector 100.Advantageously, the transparent and flexible material 112 can seal thedual-surface reflector 100 from the elements, i.e. wind, airborneparticles, dirt, bird droppings, etc. This prevents deterioration of thereflectors 104, 106 and reduces maintenance with respect to cleaning thereflectors 104, 106.

A support member 114 can be disposed to the outer perimeter support ring110 and a base 116. The base 116 can connect to a tracking mechanism 118through a rotatable member 120. The tracking mechanism 118 is configuredto continuously point the reflectors 104, 106 towards the sun byinitiating a rotation of the rotatable member 120 to rotate the base116, the support member 114 and the support ring 110. For example, thetracking mechanism 118 can include a microcontroller or the like canrotate according to location (e.g., an integrated Global PositioningSatellite (GPS) receiver, preprogrammed location, or the like), date,and time or the like. Additionally, the tracking mechanism 118 caninclude feedback from sensors that detect the position of the sun.

The base 116 can include one or more motors and electric generators 122,124. The opening 108 is connected to the base 116 to provideconcentrated solar energy from the reflectors 104, 106 to the one ormore motors and electric generators 122, 124. For a single motor andelectric generator 122, the motor and electric generator 122 ispositioned to allow the concentrated solar energy to enter working fluid(e.g., a liquid, a gas, or a phase change substance) without heating anoutside surface of the single motor and electric generator 122. The oneor more motors and electric generators 122, 124 can include a Stirlingor Rankine type of engine or variations of these.

FIG. 1 illustrates an exemplary embodiment with two of the motors andelectric generators 122, 124. This exemplary embodiment includes anoptical switch 126 and reflecting surfaces 128 to direct theconcentrated solar energy into each of the motors and electricgenerators 122, 124. Those of ordinary skill in the art will recognizethat the base 116 can include more than two of the motors and electricgenerators 122, 124 with a corresponding optical switch 126 andreflecting surfaces 128 to concentrate solar energy into each of themore than two of the motors and electric generators 122, 124. Theoptical switch 126 is configured to provide concentrated solar energyfor predetermined intervals into each of the motors and electricgenerators 122, 124.

Advantageously, the optical switch 126 enables the dual-surfacereflector 100 to input energy into each of the motors and electricgenerators 122, 124 in a pulsating manner only when needed and for aduration of time that is completely controllable. This enables thedual-surface reflector 100 to avoid wasting collected solar energy, i.e.the optical switch 126 enables the collected energy to be used in eachof the motors and electric generators 122, 124 as needed. For example,the optical switch 126 can be configured to direct collected solarenergy into a heating chamber of each of the motors and electricgenerators 122, 124 only during a heating cycle. The motors and electricgenerators 122, 124 each have offset heating cycles to allow allcollected solar energy to be used, i.e. the optical switch 126 cyclesbetween each of the motors and electric generators 122, 124 for theirindividual heating cycles.

In an exemplary embodiment, the dual-surface reflector 100 can includeinflatable components, such as an inflatable portion 130 between theprimary reflector 104 and the secondary reflector 106 and in the outerperimeter support ring 110. Air lines 132, 134 can be connected to theinflatable portion 130 and the outer perimeter support ring 110,respectively, to allow inflation through a valve 136, a pressure monitor138, and an air pump 140. Additionally, a microcontroller 142 can beoperably connected to the air pump 140, the pressure monitor 138, thevalve 136, the tracking mechanism 118, etc. The microcontroller 142 canprovide various control and monitoring functions of the dual-surfacereflector 100.

Collectively, the components 136, 138, 140, 142 can be located withinthe base 116, attached to the base 116, in the tracking mechanism 118,external to the base 116 and the tracking mechanism 118, etc. The valve136 can include multiple valves, such as, for example, an OFF valve, anON/OFF line 132/134 valve, an OFF/ON ON/OFF line 132/134 valve, and soon for additional lines as needed, or the valve 136 can include multipleindividual ON/OFF valves controlled by the microcontroller 142.

The inflatable components can be deflated and stored, such as in acompartment of the base 114. For example, the inflatable componentscould be stored in inclement weather, high winds, and the like toprotect the inflatable components from damage. The microcontroller 142can be connected to sensors which provide various feedback regardingcurrent conditions, such as wind speed and the like. The microcontroller142 can be configured to automatically deflate the inflatable componentsresponsive to high winds, for example.

The support member 114 and the outer perimeter support ring 110,collectively, are configured to maintain the desired shape of theprimary reflector 104, the secondary reflector 106, and the transparentand flexible material 112. The pressure monitor 138 is configured toprovide feedback to the microcontroller 142 about the air pressure inthe inflatable portion 130 and the outer perimeter support ring 110. Thedual-surface reflector 100 can also include controllable relief pressurevalves (not shown) to enable the release of air to deflate thedual-surface reflector 100. The transparent and flexible material 112can form a closed space 130 which is inflated through the air line 132to provide a shape of the secondary reflector 106, i.e. air is includedin the interior of the dual-surface reflector 100 formed by thetransparent and flexible material 112, the secondary reflector 106 andthe primary reflector 104.

Advantageously, the inflatable components provide low cost and lowweight. For example, the inflatable components can reduce the loadrequirements to support the dual-surface reflector 100, such as on aroof, for example. Also, the inflatable components can be transportedmore efficiently (due to the low cost and ability to deflate) and storedwhen not in use (in inclement weather, for example).

In another exemplary embodiment, the primary reflector 104, the supportmember 114, the outer perimeter support ring 110, the transparent andflexible material 112, etc. could be constructed through rigid materialswhich maintain shape. In this configuration, the components 136, 138,140 are not required. The microcontroller 142 could be used in thisconfiguration for control of the tracking mechanism 118 and generaloperations of the dual-surface reflector 100.

In both exemplary embodiments of the dual-surface reflector 100, themicrocontroller 142 can include an external interface, such as through anetwork connection or direct connection, to enable user control of thedual-surface reflector 100. For example, the microcontroller 142 caninclude a user interface (UT) to enable custom settings.

The primary reflector 104 can be made from a flexible material such as apolymer (FEP) that is metalized with a thin, highly reflective metallayer that can be followed by additional coatings that protect andcreate high reflectance in the infrared region. Some of the metals thatcan be used for depositing a thin reflector layer on the polymersubstrate material of the inflatable collector can include gold,aluminum, silver, or dielectric materials. Preferably, the surface ofthe primary reflector 104 is metalized and coated such that it isprotected from contamination, scratching, weather, or other potentiallydamaging elements.

The secondary reflector 106 surface can be made in the same manner asthe primary reflector 104 with the reflecting metal layer beingdeposited onto the inside surface of the secondary reflector 106. Forimproved performance, the secondary reflector 106 can be made out of arigid material with a high precision reflective surface shape. In thiscase the, the secondary reflector can be directly attached to thetransparent and flexible material 112 or be sealed to it (impermeable toair) around the perimeter of the secondary reflector 106. Both theprimary reflector 104 and the secondary reflector 106 can utilizetechniques to increase surface reflectivity (such as multi-layers) toalmost 100%.

The dual-surface reflector 100 operates by receiving the solar energy102 through solar radiation through the transparent and flexiblematerial 112, the solar radiation reflects from the primary reflector104 onto the secondary reflector 106 which collimates or slightlyfocuses the solar radiation towards the opening 108. One or more engines(described in FIG. 5) can be located at the opening 108 to receive theconcentrated solar radiation (i.e., using the optical switch 126 and thereflectors 128 to enable multiple engines). The collimated or focusedsolar radiation from the secondary reflector 106 enters throughoptically transparent window on the engines towards a hot end (solarenergy absorber) of a thermodynamic engine.

Advantageously, the dual-surface reflector 100 focuses the solar energy102 and directs it into each of the motors and electric generators 122,124 for their individual heating cycles in a manner that avoids heatingengine components other than the solar energy absorber element in theheating chamber of the motors and electric generators 122, 124.Specifically, the opening 108 extends to the optical switch 126 whichdirects the concentrated solar energy directly into each of the motorsand electric generators 122, 124 through a transparent window of theheating chamber. The materials forming the opening 108 and thetransparent window include materials with absorption substantially closeto zero for infrared radiation.

The dual-surface reflector 100 includes a large volume, and ispreferably suitable for open spaces. For example, the dual-surfacereflector 100 could be utilized in open-space solar farms for powerplants, farms, etc. In an exemplary embodiment, the dual-surfacereflector 100 could be four to six meters in diameter. Alternatively,the dual-surface reflector 100 could be a reduced size for individualhome-use. Advantageously, the light weight of the inflatable componentscould enable use of the dual-surface reflector 100 on a roof. Forexample, a home-based dual-surface reflector 100 could be 0.1 to onemeters in diameter. Also, the reduced cost could enable the use of thedual-surface reflector 100 as a backup generator, for example.

Referring to FIG. 2, multiple solar collectors 200 are illustrated forproviding a flatter and compact arrangement, i.e. a low-profile design,according to an exemplary embodiment of the present invention. FIG. 2illustrates a top view and a side view of the multiple solar collectors200. In the top view, the multiple solar collectors 200 can be arrangedside-by-side along an x- and y-axis. Each of the solar collectors 200includes a focusing/collimating element 202 which is configured toconcentrate solar radiation 102 into a corresponding light guide 204.The focusing/collimating element 202 is illustrated in FIG. 2 with anexemplary profile, and additional exemplary profile shapes areillustrated in FIG. 4.

The focusing/collimating element 202 focuses the solar radiation 102into a cone of light with a numerical aperture smaller than thenumerical aperture of the light guide 204. The focusing/collimatingelement 202 can be made out of a material transparent to infrared solarradiation, such as FEP. The focusing/collimating element 202 can be asolid material or hollow with a flexible skin that allows the element202 to be formed by inflating it with a gas. Forming the element thoughinflation provides weight and material costs advantages.

The light guides 204 can be constructed out of a material that isoptically transparent in the infrared region, such as FEP, glass, orother fluorinated polymers in the Teflon® family, or the light guides204 can be made out of a thin tube (e.g., FEP) filled with a fluid, suchas Germanium tetrachloride or Carbon tetrachloride, that is transparentto infrared radiation. Advantageously, the light guides 204 include amaterial selected so that it has close to zero absorption in thewavelengths of the solar energy 102. The tube material must have ahigher index of refraction than the fluid inside it in order to create astep index light guide that allows propagation of the concentrated solarradiation. The array of the multiple solar collectors 200 can extend inthe X and Y direction as needed to collect more solar energy.

The focusing/collimating element 202, the light guide 204 and theinterface 206 can be rotatably attached to a solar tracking mechanism(not shown). The tracking mechanism is configured to ensure thefocusing/collimating element 202 continuously points toward the sun. Amicrocontroller (not shown) similar to the microcontroller 142 in FIG. 1can control the tracking mechanism along with other functions of themultiple solar collectors 200. The tracking mechanism can individuallypoint each of the focusing/collimating elements 202 towards the Sun, oralternatively, a group tracking mechanism (not shown) can align a groupof elements 202 together.

Referring to FIG. 3, a mechanism 300 is illustrated for combining solarradiation 102 from the multiple light guides 204 in FIG. 2 according toan exemplary embodiment of the present invention. The multiple lightguides 204 are configured to receive concentrated solar radiation fromthe focusing/collimating elements 202 and to guide it and release itinside a hot end of one or more thermodynamic engines. Optical couplers302 can be utilized to combine multiple light guides 204 into a singleoutput 304. For example, FIG. 3 illustrates four total light guides 204combined into a single output 306 through a total of three cascadedoptical couplers 302. Those of ordinary skill in the art will recognizethat various configurations of optical couplers 302 can be utilized tocombine an arbitrary number of light guides 204. The optical couplers204 which are deployed in a tree configuration in FIG. 3 reduce thenumber of light 204 guides reaching the thermodynamic engine.Alternatively, each light guide 204 could be directed separately intothe thermodynamic engines.

An optical splitter 308 and an optical switch 310 can also be includedin the optical path (illustrated connected to a light guide 312 whichincludes a combination of all of the light guides 204) at an optimumlocation along each light guide 204 leading to the thermodynamicengines. The optical splitter 308 and optical switch 310 permitpulsation of the concentrated solar energy into multiple thermodynamicengines. Each branch (e.g., two or more branches) of the opticalsplitter 308 leads to a different thermodynamic engine. The opticalswitch 310 sequentially directs the concentrated solar energy travelingalong the light guide 312 into different arms of the optical splitter308. For example, the multiple thermodynamic engines can include offsetheating cycles with the optical splitter 308 and the optical switch 310directing solar energy 102 into each engine at its corresponding heatingcycle. Advantageously, this improves efficiency ensuring that collectedsolar energy 102 is not wasted (as would occur if there was a singleengine because the single engine only requires the energy during theheating cycle).

The optical switch 310 can be integrated into the optical splitter 308as indicated in FIG. 3 or it can exist independently in which case theoptical splitter 308 could be eliminated and the optical switch 310 canhave the configuration presented in FIG. 1 (i.e., optical switch 126 andreflecting surfaces 128). In the case where the optical switch 310 isindependent of the light guide 312, the light guide termination isdesigned to collimate the light directed towards the optical switch 310.The selection of the optimum points where the optical splitters 308 areinserted depends on the power handling ability of the optical switch 310and on economic factors. For example, if the optical switch 310 isinserted in the optical path closer to the thermodynamic engine, thenfewer switches 310 and shorter light guides 204 are needed, but theoptical switches 310 need to be able to handle higher light intensities.

Referring to FIG. 4, various designs are illustrated for thefocusing/collimating element 202 a-202 e according to an exemplaryembodiment of the present invention. The focusing/collimating element202 a, 202 b, 202 c each include an optically transparent solid material402 shaped in either a bi-convex (element 202 a), a plano-convex(element 202 b), and a meniscus form (element 202 c), all of which havethe purpose to focus the incoming solar energy 102. Additionally, eachof the elements 202 a, 202 b, 202 c also include a flexible “skin”material 404 that together with the optically transparent solid material402 form an inflatable structure 406 which can be inflated with air or adifferent gas. The air/gas pressure in the inflatable structure 406 canbe dynamically controlled to maintain an optimum focal distance betweenthe solid material 402 and the thermodynamic engine. The opticallytransparent solid material 402 and the flexible “skin” material 404 aremade out of a material transparent to visible and infrared solarradiation, such as FEP, for example. The focusing/collimating element202 d is a solid convex focusing element constructed entirely of theoptically transparent solid material 402.

The focusing/collimating element 202 e includes an inflatable dualreflector including a primary reflecting surface 408 and a smallersecondary reflecting surface 410 inside an inflatable structure 406. Theprimary reflecting surface 408 and the secondary reflecting surface 410are configured to collectively concentrate the solar radiation 102 intoan opening 412 that leads to the light guide 204. Both reflectingsurfaces 408, 410 can be rigid or flexible such as metalized films oronly the secondary reflector 410 can be made out of a rigid materialwith a high precision reflective surface shape. In this case, thesecondary reflector 410 can be directly attached to the transparentmaterial 404 or can be sealed to it (impermeable to air) around theperimeter of the secondary reflector 410. Some of the metals that can beused for metalizing a thin reflector layer on the polymer substratematerial of the inflatable collector can include gold, aluminum, silver,or dielectric materials. The preferred surface to be metalized is theinside of the inflatable solar collector such that it is protected fromcontamination, scratching, weather, or other potentially damagingelements.

Techniques to increase surface reflectivity (such as multi layerdielectric coatings) to almost 100% can be utilized. Again, the air/gaspressure can be dynamically controlled, based on feedback from pressuresensors monitoring the inside pressure of the inflatable focusingelement, to maintain the optimum focal distance. All transparentmaterials through which solar radiation and concentrated solar radiationpasses through can have their surfaces covered with broad bandanti-reflective coatings in order to maximize light transmission. Thedesigns of the focusing elements 202 presented in FIG. 3 are forillustration purposes and those of ordinary skill in the art willrecognize other designs are possible that would meet the purpose andfunctionality of the focusing elements 202.

The multiple solar collectors 200 can be utilized in buildings, such asoffice buildings, homes, etc. For example, multiple focusing/collimatingelements 202 can be placed on a roof with the light guides 204 extendinginto the building towards a service area, basement, etc. to one or morethermodynamic engines. Additionally, the light guides 204 heat up verylittle based upon their material construction. Advantageously, the lowprofile design of the solar collectors 200 enables roof placement andthe light guides enable a separate engine location within a building.

Referring to FIGS. 5A and 5B, a partial cross-sectional view illustratesa thermodynamic closed-cycle based engine 500 according to an exemplaryembodiment of the present invention. FIG. 5A illustrates an exemplaryembodiment where concentrated solar energy 102 travels through freespace to enter the engine 500 through an optically transparent window502. Also, multiple optically transparent windows 502 could be utilized.The optically transparent window 502 is made out of a materialtransparent to infrared radiation, such as sapphire, fused silica or thelike. The shape of the optically transparent window 502 is such that itfacilitates sealing of working fluid inside the engine 500 and reductionof back reflection. FIG. 5A shows a trapezoidal cross section of theoptically transparent window 502 as an exemplary embodiment. Theoptically transparent window 502 can be disposed at an end of theopening 108 or placed adjacent to the reflecting surfaces 128 of thedual-surface reflector 100 in FIG. 1.

FIG. 5B illustrates an exemplary embodiment where concentrated solarradiation enters the engine 500 through a plurality of light guides 504.Each of the light guides 504 includes a termination 506 that is made outof material transparent to infrared radiation and that is also resistantto the high temperatures inside the engine 500. The shape of termination506 facilitates sealing of working fluid inside the engine 506. FIG. 5Bshows a trapezoidal cross section of the termination 506. Thetermination 506 has an angled tip inside the engine 500 that minimizesback reflection inside the light guide 504 and also minimizes couplingback into the light guide 506 of radiation from the engine 500. Thetermination 506 includes a very hard material with good opticalproperties able to withstand high temperatures. The plurality of lightguides 504 can connect to the solar collectors 200 in FIGS. 2-4.Additionally, the engine can include fewer light guides 504 than solarcollectors 200 utilizing the mechanism 300 in FIG. 3 to combine lightguides 204.

The engine 500 can include a Stirling-type engine, a Rankine-typeengine, or the like. A Stirling engine is a closed-cycle regenerativeheat engine with a gaseous working fluid. The Stirling engine isclosed-cycle because the working fluid, i.e., the gas in a heat chamber508 which pushes on a piston 510, is permanently contained within theengine 500. This also categorizes it as an external heat engine whichmeans it can be driven by any convenient source of heat. “Regenerative”refers to the use of an internal heat exchanger called a ‘regenerator’which increases the engine's thermal efficiency compared to the similarbut simpler hot air engine.

In both FIGS. 5A and 5B, the optically transparent window 502 and theplurality of light guides 504 transfer concentrated solar energydirectly into the heat chamber 508 of the engine 500. Advantageously,this direct transfer provides a lower temperature of the engine 500 andreduced thermal stress on a body 512 of the engine 500. The engine 500can include a liner 514 made out of a material that is a reflector ofinfrared radiation and at the same time has poor thermal conductivity(thermal insulator). Advantageously, the liner 514 keeps heat inside theengine 500 avoiding excessive heating of the engine body. This leads tolonger engine life, better reliability, increased efficiency, and thelike.

The heat chamber 508 is delimited at one end by the piston 510 whichmoves in a reciprocating manner inside the engine 500. The efficiency ofthe engine 500 is improved in the present invention because the outsidetemperature of the hot end of the engine 500 is greatly reduced(compared to conventional designs) and therefore the radiated heat lossis decreased. Inside the heat chamber 508, the concentrated solarradiation is absorbed and the energy heats up the working fluid in thechamber. The working fluid can be a gas (typically pressurized), steam,a phase change material, or any other working fluid utilized inclosed-cycle thermodynamic engines. The optically transparent window 502can be shaped in a trapezoidal shape or the like to seal the heatchamber 508, i.e. through the pressurized gas. Alternatively, seals canbe located on the optically transparent window 502 or around theplurality of light guides 504.

The heat chamber 508 includes an energy absorber and gas heater 516which is designed to have a large surface area. The energy absorber andgas heater 516 is made out of a material that absorbs infrared radiationand can efficiently release it to the working fluid such as graphite orother type of carbon-based material, a suitable metal, a metal oxide, orthe like. The energy absorber and gas heater 516 can include carbon nanoparticles or other nano size particles uniformly distributed andsuspended in the working fluid.

The engine 500 also includes one or more heat exchangers for cooling thegas inside the heat chamber 508 at an appropriate time during thethermodynamic cycle. One or more linear generators or the like (notshown) can be coupled to a rod 518 of the pistons 510. Generally, thegenerators are configured to convert mechanical energy from the pistons510 into electrical energy. The electrical energy can be distributed foruse or stored for future use.

The engine 500 is shown for illustration purposes. Those of ordinaryskill in the art will recognize that the dual-surface reflector 100 andthe multiple solar collectors 200 can be utilized to concentrate anddirectly deliver solar energy into any type of engine. Of note, thepresent invention delivers concentrated solar energy directly into theheat chamber 508 to avoid heating the engine body.

Advantageously, the designs described herein enable distributedelectrical energy generation from a few kWs to 10's of kW per unit at alow cost. The present invention can directly generate AlternatingCurrent (AC) electricity without a need for inverters. Also, the presentinvention can provide heat output which can be used, for example, forspace heating, water heating, air conditioning, micro desalinationplants, and the like. The present invention provides low installationcosts and low overall maintenance costs. Additionally, the presentinvention can enable a modular design, such as adding additional solarcollectors as needed to scale energy generation.

Referring to FIG. 6, an energy distribution and delivery system 600 isillustrated for concentrated solar energy that allows the release of theconcentrated solar energy in a pulsating manner directly intothermodynamic closed-cycle based engines according to an exemplaryembodiment of the present invention. The energy distribution anddelivery system 600 is illustrated with two exemplary closed-cyclethermodynamic engines 602 a, 602 b, and those of ordinary skill in theart will recognize the energy distribution and delivery system 600 coulduse additional closed-cycle thermodynamic engines 602.

Each of the closed-cycle thermodynamic engines 602 a, 602 b includes afirst heating chamber 604 a, 604 b and a second heating chamber 606 a,606 b. The energy distribution and delivery system 600 is configured tomaximize usage of collected solar energy 102 by distributing the solarenergy 102 to each heating chamber 604 a, 604 b, 606 a, 606 b atappropriate times in their respective cycles. For example, the solarenergy 102 can be collected utilizing the dual-surface reflector 100and/or the multiple solar collectors 200 described herein.

The energy distribution and delivery system 600 includes multiplereflective disks 610, 612, 614, 616 for distributing the collected solarenergy 102. Note, these reflective disks 610, 612, 614, 616 could beincluded within a light guide, for example. Additionally, the opticalswitch and splitter described herein could provide similar functionalityto the reflective disks 610, 612, 614, 616. The reflective disks 610,612, 614, 616 are configured to either reflect or pass through thecollected solar energy 102. Additionally, each of the reflective disks610, 612, 614, 616 is configured to rotate to either reflect or passthrough the collected solar energy 102.

FIG. 6 illustrates an exemplary operation of the energy distribution anddelivery system 600. The collected solar energy 102, during a timeperiod 620 (following a dashed line A), passes through an opening of thefirst disk 610 and enters the heating chamber 604 a of the engine 602 a.During a time period 622 (following a dashed line B), the concentratedsolar energy 102 is reflected off the first disk 610, passes through thesecond disk 612, and reflects off the third disk 616 to enter theheating chamber 604 b of the engine 602 b.

During a time period 624 (following a dashed line C), the concentratedsolar energy 102 reflects off the first disk 610, reflects off thesecond disk 612, and reflects off reflectors 630, 632 to enter theheating chamber 606 a of the engine 602 a. The reflectors 630, 632 arepositioned to direct the concentrated solar energy 102, and light guidescould also be utilized. During a time period 634 (following a dashedline D), the concentrated solar energy 102 reflects off the first disk610, passes through the second disk 612 and the third disk 614, andreflects off the fourth disk 616 and reflective surfaces 640, 642 toenter the heating chamber 606 b of the engine 602 b.

The cycle can then start all over again. The energy distribution anddelivery system 600 can be used for one, two, or more engines chained ina similar fashion. The size and shape of the reflecting surfaces on eachindividual disk can be tailored for obtaining optimum performance. Forexample, the duration of the energy input in any chamber 604 a, 604 b,606 a, 606 b can be adjusted by varying the size of the reflectingsurface (or a combination of multiple reflecting surfaces) and therotational speed of the disk 610, 612, 614, 616. The energy distributionand delivery system 600 can include motors (not shown) configured torotate the disks 610, 612, 614, 616. The pulsating manner of energytransfer allows the solar energy to enter into the chamber of the engineperiodically, for a controllable period of time, similar to turning aswitch ON and OFF. Also, the energy distribution and delivery system 600can utilize the optical splitter 308 and the optical switch 310 in asimilar fashion as the reflective disks 610, 612, 614, 616 to distributethe solar energy 102.

Referring to FIG. 7, a flowchart illustrates an energy distribution anddelivery mechanism 600 for concentrating and releasing solar energy in apulsating manner directly into thermodynamic closed-cycle based enginesaccording to an exemplary embodiment of the present invention. Thedistribution and delivery mechanism 600 collects solar energy (step702). The collection step can include the mechanisms described hereinwith respect to the dual-surface reflector 100 and/or the multiple solarcollectors 200.

Next, the distribution and delivery mechanism 600 directs the collectedsolar energy to a first heat chamber in a first thermodynamic engine fora predetermined time period (step 704). The predetermined time periodcan correspond to a heating cycle for the first thermodynamic engine.After the predetermined time period, the collected solar energy isdirected to a next first heat chamber in a next thermodynamic engine foranother predetermined time period (step 706).

The distribution and delivery mechanism 600 checks if there is anotherthermodynamic engine (step 708). Here, the distribution and deliverymechanism 600 is configured to cycle through all of the thermodynamicengines to provide collected solar energy into the associated first heatchambers of each engine. If there is another engine, the distributionand delivery mechanism 600 returns to step 706.

If not, the distribution and delivery mechanism 600 directs thecollected solar energy to a second heat chamber in the firstthermodynamic engine for a predetermined time period (step 710). Then,the distribution and delivery mechanism 600 directs the collected solarenergy to a next second heat chamber in the next thermodynamic enginefor a predetermined time period (step 712).

The distribution and delivery mechanism 600 checks if there is anotherthermodynamic engine (step 714). Here, the distribution and deliverymechanism 600 is configured to cycle through all of the thermodynamicengines to provide collected solar energy into the associated secondheat chambers of each engine. If there is another engine, thedistribution and delivery mechanism 600 returns to step 716. If not, thedistribution and delivery mechanism 600 can return to step 704 foranother cycle through each of the heat chambers.

Referring to FIG. 8, a flow chart illustrates a mechanism 800 to convertsolar energy into electric energy according to an exemplary embodimentof the present invention. The mechanism 800 includes continuouslypositioning one or more solar collectors towards the sun (step 802).Collecting solar radiation at each of the one or more solar collectors(step 804). Directing the collected solar radiation to a heat chamber ina thermo-dynamic engine (step 806). Periodically and controllablyheating a working fluid in the thermo-dynamic engine with the directedsolar radiation (step 808). Reciprocating a piston responsive topressure changes in the working fluid (step 810). Converting themechanical motion of the piston into electrical energy (step 812).Cooling the working fluid (step 814), and repeating the mechanism 800.

Although the present invention has been illustrated and described hereinwith reference to preferred embodiments and specific examples thereof,it will be readily apparent to those of ordinary skill in the art thatother embodiments and examples may perform similar functions and/orachieve like results. All such equivalent embodiments and examples arewithin the spirit and scope of the present invention and are intended tobe covered by the following claims.

1. A dual-surface reflector for collecting solar energy, thedual-surface reflector comprising: a primary reflector; a secondaryreflector configured to receive solar energy reflected from the primaryreflector and concentrate the solar energy to a point; an opening in theprimary reflector, wherein the concentrated solar energy is provided bythe secondary reflector to the opening; and a mechanism coupled to theopening configured to directly provide the concentrated solar energy toworking fluid to avoid heating an outside surface; wherein the primaryreflector and the secondary reflector each comprise inflatablecomponents configured to inflate and deflate, and wherein the mechanismis configured to provide the concentrated solar energy external to theinflatable components.
 2. The dual-surface reflector of claim 1, furthercomprising: a switch located at the opening, wherein the switch isconfigured to distribute the concentrated solar energy directly to heatchambers of two or more thermodynamic engines.
 3. The dual-surfacereflector of claim 1, further comprising: a support ring disposed aroundthe edges of the primary reflector, wherein the support ring isconfigured to maintain a shape of the primary reflector.
 4. Thedual-surface reflector of claim 1, further comprising: a transparent andflexible material disposed between the primary reflector and thesecondary reflector, wherein the transparent and flexible material issubstantially optically transparent in the infrared region.
 5. Thedual-surface reflector of claim 4, wherein the transparent and flexiblematerial forms a seal between the primary reflector and the secondaryreflector providing protection from external elements.
 6. Thedual-surface reflector of claim 4, wherein the transparent and flexiblematerial comprises fluorinated ethylene propylene.
 7. The dual-surfacereflector of claim 1, further comprising: a base supporting the primaryreflector; and a tracking mechanism to point the primary reflectortowards the sun, wherein the primary reflector configured to move in amulti-axis configuration.
 8. The dual-surface reflector of claim 1,further comprising: an air pump configured to inflate the inflatablecomponents.
 9. The dual-surface reflector of claim 8, furthercomprising: a valve for connecting the air pump to the inflatablecomponents and for deflating the inflatable components; amicrocontroller configured to control the air pump and the valve. 10.The dual-surface reflector of claim 1, wherein the primary reflector andthe secondary reflector each comprise fluorinated ethylene propylenewith a thin, highly reflective metal layer.
 11. A dual-surfaceinflatable reflector for collecting solar energy, the dual-surfaceinflatable reflector comprising: an outer support ring; a primaryreflector disposed to the outer support ring; a secondary reflectorconfigured to receive solar energy reflected from the primary reflectorand concentrate the solar energy to a point, wherein the secondaryreflector is disposed to a transparent and flexible material disposed tothe outer support ring; and an opening in the primary reflector, whereinthe concentrated solar energy is provided by the secondary reflector tothe opening; a light guide coupled to the opening configured to directlyprovide the concentrated solar energy to working fluid to avoid heatingan outside surface; and inflation means for inflating and deflating theouter support ring and an interior formed between the primary reflector,the opening, the secondary reflector, and the transparent and flexiblematerial, wherein the light guide is configured to provide theconcentrated solar energy external to inflatable components.
 12. Thedual-surface inflatable reflector of claim 11, further comprising: solartracking means for pointing the primary reflector towards the sun. 13.The dual-surface inflatable reflector of claim 11, further comprising:switching means for distributing the concentrated solar energy directlyto heat chambers of two or more thermodynamic engines.
 14. Thedual-surface inflatable reflector of claim 11, wherein the transparentand flexible material forms a seal between the primary reflector and thesecondary reflector providing protection from external elements.
 15. Thedual-surface inflatable reflector of claim 14, wherein the transparentand flexible material comprises fluorinated ethylene propylene.
 16. Amethod of operating a solar collector, the method comprising: inflatinga reflector with a pump, the reflector is configured to inflate anddeflate; positioning the reflector towards the sun; collecting solarenergy with the reflector; concentrating the solar energy to a point atan opening; and distributing using light guides the solar energydirectly to working fluid in heat chambers of two or more engines in apulsating manner thereby preventing heating of an outside surface. 17.The method of claim 16, further comprising: deflating the reflectorresponsive to one of a deactivation signal and a determination ofinclement weather.
 18. The method of claim 17, further comprising:storing the reflector in a base.
 19. The method of claim 16, wherein thereflector comprises: a primary reflector; a secondary reflectorconfigured to receive solar energy reflected from the primary reflectorand concentrate the solar energy; and an opening in the primaryreflector, wherein the concentrated solar energy is provided by thesecondary reflector to the opening; wherein the primary reflector andthe secondary reflector each comprise inflatable components, and whereinthe primary reflector and the secondary reflector are inflated by airbetween one another, the air causing the primary reflector and thesecondary reflector to maintain shape with the concentrated solar energyused to heat the working fluid external to the inflatable components.20. The method of claim 19, wherein the primary reflector and thesecondary reflector each comprise fluorinated ethylene propylene with athin, highly reflective metal layer.